The present disclosure relates to heart valve replacement and, more specifically, to devices, systems and methods for implanting a collapsible prosthetic heart valve in a patient.
A healthy aortic valve acts as a one-way valve, opening to allow blood to flow out of the left ventricle of the heart, and then closing to prevent blood from flowing back into the heart. Diseased or damaged aortic valves may not close properly and thus allow blood to flow into the heart. Damage to aortic valves may occur due to congenital defects, the natural aging process, infection or scarring. Diseased or damaged aortic valves sometimes need to be replaced to prevent heart failure. In such cases, collapsible prosthetic heart valves may be used to replace the native aortic valve.
Current collapsible prosthetic heart valve designs may be used in high-risk patients who may need a cardiac valve replacement, but who are not appropriate candidates for conventional open-chest, open-heart surgery. These collapsible and re-expandable prosthetic heart valves can be implanted transapically or percutaneously through the arterial system. One percutaneous delivery method entails introducing a collapsible prosthetic heart valve through a patient's femoral artery. This delivery method is referred to as a transfemoral approach.
A collapsible prosthetic heart valve may be delivered into a patient via a tube-like delivery apparatus such as a catheter, a trocar, a laparoscopic instrument, or the like. To place such a valve into a delivery apparatus and ultimately into a patient, the valve must first be collapsed or crimped to reduce its circumferential size. The delivery apparatus is then introduced transapically or percutaneously into a patient until it reaches the implantation site.
When a collapsed heart valve has reached the desired implantation site in the patient (e.g., at or near the annulus of the patient's heart valve that is to be replaced by the prosthetic valve), the prosthetic heart valve can be released from the delivery apparatus and re-expanded to its full operating size.
While various improvements have been made to collapsible prosthetic heart valve delivery devices, conventional delivery devices, systems, and methods still suffer from some shortcomings. For instance, conventional delivery systems may not properly align the prosthetic heart valve with the valve annulus. A misaligned prosthetic heart valve may cause paravalvular (PV) leaks.
As stated above, collapsible prosthetic heart valves may be delivered to the valve annulus, and particularly the aortic valve annulus, either transfemorally or transapically. With either technique, however, it is difficult to properly align the collapsible heart valve with the valve annulus.
In transfemoral valve implantation, the collapsible prosthetic heart valve is delivered in a retrograde manner from the femoral artery through the aortic arch to the native aortic valve annulus. The distal sheath of the delivery catheter is bent significantly to pass through the aortic arch, which significantly biases the sheath toward the outside wall of the aortic arch. This may cause the prosthetic heart valve to be deployed out of alignment with the aortic annulus. One way to solve this problem is to employ a steerable catheter. Steerable catheters, however, can be expensive to make and more complicated to use. Another problem with steerable catheters is that the section that has to be deflected is on the distal sheath of the delivery system. It is very difficult to deflect the distal sheath because the collapsible prosthetic heart valve is stored therein. It is therefore desirable to have systems and methods which can effectively improve the alignment of the deployed valve with the aortic annulus without significantly changing the delivery system.
In transapical valve implantation, the collapsible prosthetic heart valve is delivered in an antegrade fashion through the apex of the heart. In order to place the prosthetic heart valve accurately at the desired location in the aortic annulus, the collapsed heart valve should first expand at its annulus end. In the transapical approach, expanding the annulus end of a self-expanding prosthetic heart valve first requires the distal sheath of the delivery system to move distally toward and into the aortic arch. To allow for such movement, it is important to make the distal sheath with sufficient flexibility to accommodate the curve of the arch. On the other hand, the distal sheath should also have enough columnar strength to be able to withstand the resheathing force should resheathing become necessary. Ideally, the distal sheath design of the delivery system should strike a balance between flexibility and columnar strength. Conventional delivery systems still need to improve such balance.